In episode #42, Paul talks with consultant cardiologist Dr Sanjay Gupta on a subject that he specialises in, cardiac imaging.
Dr Gupta explains everything about these techniques that patients need to know and also talks about how future tools may help prevent the main cause of sudden cardiac deaths – heart attacks.
#042 Visualising the heart with Dr Sanjay Gupta
Paul Swindell: [00:00:00] Hello and welcome to another episode of the life after cardiac arrest podcast with me, your host, Paul Swindell.
And today I'm joined by Dr Sanjay Gupta, who is a consultant cardiologist at York teaching hospital, in the North of England. He also is a very popular on social media and you'll have seen him possibly doing, YouTube videos and Facebook videos on all sorts of cardiac related matters and he has a specialist interest in cardiac imaging, which we will be talking about today.
. So, welcome Dr Gupta and nice to speak with you again.
Dr Sanjay Gupta: [00:00:46] Thank you so much for having me.
Paul Swindell: [00:00:48] So cardiac imaging.
So what are we talking about there?
Dr Sanjay Gupta: [00:00:52] We're talking about, modalities which allow us to visualize the heart and the arteries surrounding the heart.
So visualizing the heart, both, to make a diagnosis, to tell you about the health of the heart, and to also guide you, about prognosis.
Paul Swindell: [00:01:14] So what are the, tools that you use?
What have you got in your toolbox ?
And, why would someone need to go through those processes that you do?
Dr Sanjay Gupta: [00:01:22] So, common modalities include echocardiography, ultrasound of the heart, CT scanning of the heart. MRI scanning of the heart, and also, radio nuclear imaging of the heart, so perfusion scanning, et cetera.
Okay, so the first thing to say is that by far and away the commonest and the most easily accessible tool we have this echocardiography.
One of the unique things about the heart is it's a moving structure and therefore, to try and understand it. you have to have moving images and that is different from say, imaging the liver or imaging the brain.
Echocardiography uses ultrasound waves, which bounce off different structures of the heart and produce a moving image on a screen.
It's very easily accessible, is available in every hospital and it offers a crude, but, well validated way to assess the structure of the heart. So, on echocardiography, you can see the heart, you can see the heart valves, you can see the size of the chambers of the heart.
You can work out whether there's any leaking of the valves, whether there's any tightness of the valves and you can see whether the function of the heart is strong or weak. And what we do know is from all the studies that if you have a structurally normal heart on the echocardiogram, then in general that points to an excellent prognosis and if you have damage to the heart or if the heart is weak on the echocardiogram, then that points your worst prognosis.
Paul Swindell: [00:03:01] And the echocardiogram, am I right in thinking these are similar tools to what the you use on a pregnant lady to look at the fetus
Dr Sanjay Gupta: [00:03:09] Absolutely, exactly the same.
Paul Swindell: [00:03:12] So that's a noninvasive procedure and you just typically put some gel on someone don't you?
Dr Sanjay Gupta: [00:03:17] You, put some jelly on the, on the patient, and then, you have this transducer and the transducer will emit, sound waves and the sound waves will hit different structures and bounce back.
And that will create an image on the screen, it can also, it is also useful in terms of working out which way blood is flowing. So, for example, if you close your eyes, you can tell usually whether an ambulance is coming towards you or going away. This is the Doppler principle. And so if you can use that information and convert it into a colour signal, you can then see where the blood is coming towards you or going away.
And that then tells you whether valves are leaky or functioning normally.
Paul Swindell: [00:04:03] Oh okay. I see. That's clever.
So you said that it's quite accurate at determining whether someone's got a functionally correct heart?
Dr Sanjay Gupta: [00:04:11] Yeah, I mean, I think it's a, I think it's still a crude test, but, there's two things.
One, it's well validated.
A lot of all the major research studies have shown that actually, you know, the information it gives, does, point towards prognosis. It's the gold standard in terms of trying to make a diagnosis of something like heart failure where the heart is weak or not.
All valvular problems, the echocardiogram is a very good way of determining, the nature of the problem, the severity of problem, and may also help you work out the best treatment for the problem.
Paul Swindell: [00:04:47] And presumably before that you would have done a, I know it's not, an imaging test, but a 12 lead ECG.
Dr Sanjay Gupta: [00:04:55] Yeah, so the 12 lead ECG is telling you something different, right?
12 lead ECG is just telling you about the electricity through the heart. So it is just telling you, about the electricity and you are making assumptions based on those electrical patterns.
With an echocardiogram you're actually looking at the heart.
So with a 12 lead ECG, if you had a valve and your valve was, let's say, very narrowed, that would cause the heart to become more muscular because it would have to generate more force against that narrowed valve. The heart would become more muscular, which means the electricity would have to go through a thicker heart muscle, and you would get much bigger complexes on the ECG.
So if you saw bigger complexes on the ECG, you would say, okay, that looks like it's a more muscular heart, which means that it could be due to this or that.
It didn't really give you the diagnosis, it just told you, but the heart had changed this way, based on the, electricity through the heart muscle.
With the echo, you're actually visualizing the heart.
So, a far better way, you're actually seeing, you can actually measure the thickness of the heart and you can look at the valves, et cetera.
So, yeah, in the old days, we didn't really have very much at all to determine what was going on, but, since echocardiography has come along and, now we have more complex echocardiographies. So previously we just used to have something called M mode echocardiography, then change it two dimensional echocardiography. Now we have three dimensional echocardiography.
So that has really revolutionized how we diagnose certain conditions, and how we monitor conditions, because it is accessible.
You know, the machines are not that expensive.
There's a lot of expertise on how to, you know, experienced staff, et cetera. It doesn't require, really, it doesn't require very, very highly specialized, just because it's so much more accessible. So, echocardiography is the kind of staple investigation.
And from my perspective, if the first test I would do, if I was worried about someone would be an echocardiogram.
If they have a strong heart, I feel relieved. If they have a weak heart, I get more worried.
Paul Swindell: [00:07:02] And so what would you progress to next if, the echocardiogram hasn't told you what you needed to know or shown that there's a problem there, but you need a little bit more detail, where would you go next?
Dr Sanjay Gupta: [00:07:14] The echocardiogram is like if you thought of the heart as a car. The echocardiography is looking at the engine of the car.
It doesn't tell you what the arteries that supply the blood to the heart look like. So with an echocardiogram, you can't see the heart arteries. You can't tell whether the heart arteries are narrowed or anything.
All you can tell is that there's been no damage to the heart.
So if you wanted to visualize the heart arteries then the next step would be to do something called cardiac CT, CT scanning, which has now become the gold standard for looking at heart arteries, you know, for the majority of patients with chest discomfort, and with cardiac CT, what you're doing is you're delineating the heart arteries themselves, and that will then tell you whether the heart arteries are narrowed or whether there are any blockages, et cetera.
Paul Swindell: [00:08:07] So , CT, what does that stand for?
And again, is this an invasive procedure ?
Dr Sanjay Gupta: [00:08:13] No, it's a noninvasive procedure and CT stands for computer tomogram or a cat scan. That's, you know, how people recognize it, but basically it involves going through a scanner. The is heart slowed down because again, the heart is a moving structure, and if you want to visualize the arteries, if you don't slow the heart down, then the arteries will move with the heart and you'll get blurred images.
So what they try and do is they slow the heart down.
And therefore in that short period of time when the heart is very slow, they're trying to image these arteries. The arteries are imaged by giving the person a contrast through one of their veins, contrast agent. And that contrast agent goes through the vessels and you can then take pictures of the heart arteries.
Paul Swindell: [00:09:00] Okay, sounds like, is it a little bit more expensive piece of equipment?
Dr Sanjay Gupta: [00:09:04] Definitely, not all centers have access to cardiac CT.
Currently the guidance says that if you, for example, came and said to me, look, I'm getting chest pain. And I'm like, you know, I would say, well, I'm not quite sure.
Maybe it could be your heart.
Maybe it couldn't be.
Maybe it isn't your heart.
What tests should we do?
The current guidance is that the majority of those patients should have a cardiac CT. And a cardiac CT is an exceptionally good test in terms of if your heart arteries are normal, it's probably the best test we have out there that tells us that if your heart arteries looked normal in the cardiac CT, then the chances of something bad happening to you are really, really low.
It's not so good if you have abnormalities because you still then need to image it further. Because what tends to happen is a lot of times when you get buildup of plaque and disease in the, in the blood vessels, you get deposition of calcium and calcium reflects rays.
So what, what then happens is, you know, when you're doing the cardiac CT, you get these bright bits of calcium and you can't see beyond them because of the calcium.
So when you see a lot of kind of calcium in the heart arteries, one, it tells you that the arteries are diseased, but then you have to do a better test or a more invasive test to see exactly how bad the narrowings are beyond those lumps of calcium, which are in some way blurring the image because they're reflecting these.
It's like taking a flash photograph in front of a mirror. You get a, you know, you get that bright light hitting you back. and so, in that setting, if, if you have an abnormal cardiac CT, most people would then go on and do something called an invasive angiogram.
Which actually involves putting a needle into either the groin or the the wrist and passing a tube all the way to the heart, and then squirting some dye into that tube that dye that fills up the heart arteries and then you take x-rays.
That way you're purely looking at the heart arteries that actually lumen of the heart arteries, and that is the gold standard kind of invasive test for coronary disease.
Paul Swindell: [00:11:16] So with the CT and the angiogram, you're not actually looking at the heart, you're just looking at the
Dr Sanjay Gupta: [00:11:22] Artery
Paul Swindell: [00:11:22] Arteries around it.
Dr Sanjay Gupta: [00:11:23] Yeah, exactly, exactly.
Paul Swindell: [00:11:25] Okay.
Dr Sanjay Gupta: [00:11:26] If we wanted the heart and more details, so you know where you have the echocardiogram, is there another test which can offer you the same thing but in a lot more detail?
And the answer is yes.
That's where you go to cardiac, magnetic resonance imaging, cardiac MRI.
Cardiac MRI, allows a much better visualization of the heart, but obviously it's a much more sophisticated procedure, it involves the patients having to go in this very claustrophobic tunnel for about an hour with lots of noise and clanging, but it is a test which allows excellent visualization of the heart.
One other thing which is really useful for you to know, I guess, is that, there was a series of experiments. Done in America where they took a bunch of dogs and they occluded the heart arteries and they studied the damage that was done to the heart when they occluded the heart arteries.
When you create a heart attack, what is the pattern of the damage that occurs in the heart?
And what they found is that all damage caused by heart attacks goes from inwards, outwards, so from within the heart, outwards. The inner most layer is always affected first.
With cardiac magnetic resonance, you can give a dye called gadolinium and that can delineate scar that accumulates in scar. And so if you then take the images and you find that that scar is involving the inner most layer, then you make a good assumption that that scar was caused by a heart attack. So in that sense with an echocardiogram, all you see is a bit that's not moving and you assume that there's been damage.
But what we don't know for sure, and sometimes we cannot be sure is was that because the person that had a heart attack was that because the person had a virus? Was that because of something else?
And MRI is very good because it delineates exactly the nature of the damage and the pattern of the damage by gives you a good clue as to why that may have happened in the first place.
Paul Swindell: [00:13:27] Can you do a, an MRI or a moving MRI of the heart? Like you, like you said, the echo-cardiogram, you can see the blood moving and whether it's going in the right direction, what have you, do you get that similar sort of picture from the MRI.
Dr Sanjay Gupta: [00:13:43] Yeah again, with an MRI you get, you can get moving images and, so you can see the function of the heart, you can see the function of the heart better than with echocardiography. It's not so good for looking at the way blood moves in and out in the valves, et cetera. But people are developing a MRI and you know it's coming along, but in that sense, echocardiography is probably still better to look at the heart valves and you know, the, the actual physiology to study physiological changes within the heart I think echocardiography is still better.
But echocardiography has a problem, you know, not everyone has the best pictures. You know, you have to get a window and some people carry extra weight or who have ribs very close together. You may not necessarily get any kind of decent pictures to be able to make, any kind of assessment of their hearts.
MRI doesn't have those constraints.
So with MRI, you're not so worried, you can still visualize the heart very well.
Paul Swindell: [00:14:43] So it sounds like all of them have a part to play in your toolbox as it were. The they, they will show you something slightly different.
Dr Sanjay Gupta: [00:14:51] Absolutely. I mean, there are anatomical tests.
There are functional tests, there are tests for the heart arteries, and then there are tests with the actual heart itself, the heart muscle.
Paul Swindell: [00:15:02] So is there anything, anything else that you might do or this is something else that you'd like, that isn't invented yet?
Dr Sanjay Gupta: [00:15:10] So in the old days, what we used to think is if the heart looks okay on the heart scan, on an echocardiogram, then the person doesn't have heart failure, for example. You know the heart, if the heart looks okay on an echocardiogram, then it's not your heart. So someone comes in and says, oh, I'm getting more and more breathless, my legs are filling up with fluid. Those are typical signs of the heart being weak, but if you then did the echocardiogram and the found that the heart was strong, then most people would turn around at that point and say, no, that's not your heart.
Now they're beginning to realize that actually there are some people who have what may look like a normal heart on the scan, but may still have signs of heart failure. And actually when you follow these people up, they do badly in the long run anyway. And so we're beginning to realize that we've used a two dimensional modality to study a very complex three dimensional structure.
You know, the heart will move.
When the heart contracts, it contracts in different ways.
It contracts radially.
It contracts longetudinally it contracts, it twists and turns.
But the modalities we're using are only looking at one movement. And therefore, I think, we are beginning to realize that sometimes our tests have their own kind of limitations, but it is that recognition which will allow us to move forward and identify new modalities, which will help us determine, what's going on with the heart.
The other thing of course, to say is that most of these are a visual impression. You know, you're just looking at the heart, right?
You haven't gone inside the heart. You haven't studied in under a microscope.
So can the heart still be diseased if it looks normal?
And the answer is yes, it can still be diseased, even if it looks normal.
This is the fundamental problem when we hear about people like, athletes you know, who are playing football and then suddenly dropped down, dead on the pitch.
I mean, these guys have been investigated, they've gone through medical screening, I'm sure they've come through a whole manner of tests. And so it is always sort of something that is very worrying when someone like that suddenly drops down dead because you say, well, he had all the tests, they were all normal, why did this happen?
And the answer is because we are only basing our assessments on a visual interpretation. We haven't actually taken the heart, looked at it under a microscope. We don't know. You know, we can only look for things that are causing an outward change in appearance.
Paul Swindell: [00:17:42] I guess the heart isn't an under stress as well when you're doing these tests either.
Dr Sanjay Gupta: [00:17:47] We do something called stress echocardiography, so where you can actually look at the heart and then you put the person on a treadmill and make the heart beat really, really fast, and then you bring them off and study the heart again, and that's a good way of assessing, well, the strength of the heart.
And those aren't, those aren't, you know, those are relatively straightforward. It is that kind of patient like yourself, you know, when you mentioned that looking at out of the blue, suddenly, you know, one day you're out.
Why did that happen?
What was there anything that could have determined that that was going to happen beforehand?
And the reality is probably not.
And those are the groups of patients we need to study better and we need to develop more, advanced, modalities, which allow us to determine, you know, determine risk. I think, I think what we have is a good tools, for a population to study a population.
Are we very good at using those tools to study an individual? And that's a bit more difficult, you know, because the reality is anyone anywhere can have something bad happens to the many ones suffer cardiac arrest at any point.
What we are doing is we're saying, okay, well if you've got a strong looking heart, then you in general belong to that population is going to do well.
Paul Swindell: [00:19:00] And so you talked about these other modalities , do you know of any technologies that are coming along?
Dr Sanjay Gupta: [00:19:05] I think there'll be metabolic imaging is a very interesting field.
So one of the very interesting things that the big problem by far as heart attacks, that is the, by far the biggest killer, right? So sudden heart attacks, heart attacks, which come out of the blue, they, they're responsible for the majority of sudden deaths.
And, the, the question is why two heart attacks occur?
And, you know, the general kind of understanding certainly amongst the public is that you get narrowing. So if your heart arteries, the heart arteries get narrower and narrower and one day one blocks off and that causes the heart not to get the blood, it gets damaged.
The heart misbehaves because it's not getting any blood and the person drops down dead. The reality is. when you look at the, or, our understanding has changed because what we're starting to realize this, not all people who have significant narrowings are going die because that narrowing has blocked off.
Sometimes people don't have significant narrowings. They have a may have a very, very minor narrowing and one day, for whatever reason, that particular area, that little clot breaks off. And the body thinks you've sustained a wound and forms a blood clot to try and heal that wound and the blood clot inadvertently blocks of the vessel and stops the blood getting to the heart, which causes the heart attack.
And that can occur within a matter of two or three minutes.
Paul Swindell: [00:20:29] Oh wow. I didn't realize it was that quick.
Dr Sanjay Gupta: [00:20:31] Yeah. So those are the people. You see that there are two groups of people. There'll be those people who will say, I've been getting chest pain every time I walk, I walk. So I went to see my doctor. My doctor did a test.
He said, I have 99% blockage in, says I need an emergency bypass. Thank God I have the bypass. It saved my life. The reality is actually when you look at all the data, bypasses and stents done in that kind of non-acute setting have not been shown to prolong life. So the question is why have they not been shown to prolong life.
And the answer is because that narrowing was probably not the narrowing that was going to kill that patient. The patients, a lot of patients die because they get unstable clot, which may not be causing a narrow, and that unstable clot chooses to break off. If you think about it, you get cold clots, which are nice sort of clots, which have been there for a long time.
They're like, cement. They're not, they're not fragile, they don't break off. And then you have hot plaque, which is a lot more, a lot more fragile, a lot more inflamed, and one chooses to break off. And that's where you get that sudden, the patient who is completely fine and boom, dead. so when you image the heart at the moment, anatomical imaging is only largely geared towards trying to identify the narrowest bits.
It doesn't identify the bits that are most likely to break off.
So if in some way you can develop techniques which identify which plaques are hot and which plaques are cold, then you can start treating hot plaques. And if you treated hot plaques may be the risk of sudden death from heart attacks will go less.
Paul Swindell: [00:22:15] I see. That sounds good.
Is that feasible, do you think?
Dr Sanjay Gupta: [00:22:19] I think so. I think because, I think there's, you know, the, the hot plaque tend to be more inflamed. They tend to be newer. So the process is going on with a hot plaque are a different, I think there are centers, there's a center in Oxford that has an interest in this, so I think that would be a really interesting thing.
The problem at the moment is, you know, stents and bypasses are only done for the narrow bits. Right? Because if you, if you don't have a narrowing, then if you bypass the narrowing, there's no reason the blood will go down the bypass because there's no real narrowing. So the blood will choose to go down where it's always gone down and the bypass would fail.
Similarly, if you stent something which is not narrowed, you don't derive any benefit.
So, of course, it'd be one thing to try and identify hot plugs and then it would be another thing to try and say, well, how would you go about treating these hot plugs?
How would you make these hot plugs colder?
And I think that would be a very interesting field.
Paul Swindell: [00:23:15] Topic for another podcast, I think.
Well, I think there's a topic for a lot of researchers and probably a lot of money as well.
Dr Sanjay Gupta: [00:23:23] I think it's a very interesting field. I think that's, I think is the most important thing that's come out in my understanding of cardiology, which is, you know, the bits that we think are the most threatening tend, you know, the people die of things, which can actually look relatively innocuous, but then choose to misbehave rather than something that looks ugly.
Because it's, long standing things are unlikely just to suddenly cause a problem, whereas something that is relatively acute, something which is very hot, as much more likely to be dangerous.
Paul Swindell: [00:23:56] Okay.
Have you got anything else to add in this imaging arena?
Anything you'd like to impart, or have we said it all basically?
Dr Sanjay Gupta: [00:24:06] I think we've said it all, no, I think we've said it all.
I can't think of anything else.
Paul Swindell: [00:24:10] So in general, cardiac imaging patients should never be really worried about them cause they're either noninvasive or minimally invasive.
You might have to have an injection or something like that.
Dr Sanjay Gupta: [00:24:23] Yeah. I think this is the real advantage with noninvasive modalities because, you know, they offer a high yield, low risk and the invasive ones are generally only done when the patient really, really needs them now, not an ad hoc so to speak.
So there's a lot to be said. I mean, we've moved, you know, as cardiac CT is incredible. It's to be able to visualize the heart arteries in this way, and to have a test which has been shown that if it's normal, it portends to really good patient outcomes is really reassuring.
Paul Swindell: [00:24:55] Well. That's brilliant.
Thank you very much, Dr Gupta for that really interesting overview of all of the types of imaging that patients might expect to encounter if there are ever become a cardiac patient.
And thank you very much again for your time. It's been really enjoyable.
Thanks a lot.
Dr Sanjay Gupta: [00:25:15] Thank you so much. I've enjoyed it.
Paul Swindell: [00:25:19] This concludes this episode of the life After Cardiac Arrest podcast, and I'd love to know what you think. And you can do that via Facebook, Twitter, Instagram, or the website, SuddenCardiacArrestUK.org and you can find this by Googling Sudden Cardiac Arrest UK or the Life after cardiac arrest podcast.
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Presented and edited by Paul Swindell.
Recorded March 2020.